#include <stdio.h>

double fact(int N) {
	if(N==0 || N==1)
		return 1;
	int i;
	long sol = 1;
	for(i=2; i<=N; i++)
		sol *= i;
	return sol;
}

long get_count(int P) {
	long count=0, i, N, tmp;
	N = 5*P;
	i=5;
	while (i<N && count<P) {
		count++;
		tmp = i/5;
		printf("i=%ld  count=%ld   tmp = %ld\n", i, count, tmp);
		while(tmp%5==0 && tmp>0) {
			count++;
			tmp = tmp / 5;
		}
		if(count<P)
			i+= 5;
	}
	if(count>P)
		return -1;
	return i;
}

int main(int argc, char *argv[]) {
	
	long P, N, h;
	
	printf("argc = %d argv[0] = %s\n", argc, argv[0]);
	if(argc==2) {
		N = atoi(argv[1]);
		printf("%ld ! = %f\n", N, fact(N));
	}

	FILE *f1 = fopen("fact.in", "r");
	fscanf(f1, "%ld", &P);
	fclose(f1);	

	f1 = fopen("fact.out", "w");
	
	N = get_count(P);

/*	
	N = 5*P;
	if(N<25) {
		fprintf(f1, "%d\n", P>0?N:1);
	} else if(N<125) {
		fprintf(f1, "%d\n", N-5);
	} else if(N<625) {
		h = N/25;
		fprintf(f1, "%d\n", );
	}
*/	
	fprintf(f1, "%ld\n", P>0?N:1);
	fclose(f1);	
	
	return 0;
}